Moral relativism.

From Google;

<<Protagoras' notion that "man is the measure of all things" may also be seen as an early philosophical precursor to relativism>>

What exactly does that even mean? Can you explain?

Moral relativism means realising that morals are axiomatic structures. Once that is realised one realises that there are no absolute morals, morals are relative to culture.

I'd have to look into it more. Many philosophers put forth this idea. Many used Einstein's Theory of Relativity to spring board in to the theory of moral relativism. I think that is a mistake. Emotions, mindsets, tastes etc are relative. However, just like the periodic table is not relative so are proper morals. I don't know of a culture were cowards and rapist are honored. If they are honored then that culture will not sustain itself.

You ?

See, you just defined moral as that which sustains the culture. That is an axiom, and from that axiom you deduct that rapists and cowards should not be honored.